I have a white crested black polish (Sophie) and a silver laced polish (Panni) in a mixed flock currently. They are most definitely submissive to the rest of the flock, and the white crested was picked on horribly. I currently have her inside, while she grows the feathers back on her head (something attracts the others to the white crest feather, which may be similar with a buff laced). Size wise, they are a good 1-2 pounds smaller than the rest of my flock, so they are easily pushed around. My husband (as we speak/write) is building a separate coop for my polish. I can't risk Sophie being picked on so severly again, and Panni is pushed around as well.
If you want polish, I'd suggest getting all polish. They are very cute, and mine are the friendliest of my birds (except my golden laced wyandotte). I think people see them as flighty because they can act spooky. But, in my opinion,that's just because they can't really see what's sneaking up on them until it's really close. I love my polish, and wouldn't get rid of them for anything. But, if I could do it again, I would have all polish. Good luck with your decision.